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arXiv · 0909.4208

Intermediate-valence behavior of the transition-metal oxide CaCu$_3$Ru$_4$O$_{12}$

A. Krimmel·A. Günther·W. Kraetschmer·H. Dekinger·N. Büttgen·V. Eyert·A. Loidl·D. V. Sheptyakov·E. -W. Scheidt·W. Scherer
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Abstract

The transition--metal oxide CaCu$_3$Ru$_4$O$_{12}$ with perovskite--type structure shows characteristic properties of an intermediate--valence system. The temperature--dependent susceptibility exhibits a broad maximum around $150 - 160$ K. At this temperature, neutron powder diffraction reveals a small but significant volume change whereby the crystal structure is preserved. Moreover, the temperature--dependent resistivity changes its slope. NMR Knight shift measurements of Ru reveal a cross--over from high temperature paramagnetic behavior of localized moments to itinerant band states at low temperatures. Additional density--functional theory calculations can relate the structural anomaly with the $d$--electron number. The different experimental and calculational methods result in a mutually consistent description of CaCu$_3$Ru$_4$O$_{12}$ as an intermediate--valent system in the classical sense of having low--energy charge fluctuations.

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A. Krimmel, A. Günther, W. Kraetschmer, H. Dekinger, N. Büttgen, V. Eyert, A. Loidl, D. V. Sheptyakov, E. -W. Scheidt, W. Scherer. 2009-09-23. Intermediate-valence behavior of the transition-metal oxide CaCu$_3$Ru$_4$O$_{12}$. https://doi.org/10.1103/physrevb.80.121101

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